Description of problem:
I install Fedora from a USB stick (sda) to a machine hard drive (vda). In a dialog I select USB stick to be "data storage device" and machine hard drive to be "install target device", see anaconda1.png. But later on I choose Custom layout and try to create a new PV partition. Anaconda by default lists and selects both my devices in "Allowable Drives" field, see anaconda2.png. If I hit continue, it complains, see anaconda3.png.

Now, why is the USB stick present in the Allowable Drives field, if I didn't mark it as "install target device"? Is that a bug? I don't understand why anaconda offers me that when I clearly said I don't want to install anything there.

The USB stick layout is also displayed in the partitioning screen (visible in the background of anaconda2.png or anaconda3.png). Again, should it be there when I didn't mark it as "install target device"?

Version-Release number of selected component (if applicable):
anaconda 17.20
F17 Beta

How reproducible:
always

Steps to Reproduce:
1. install from USB stick created by livecd-iso-to-disk
2. select only your hard drive as install target device
3. see usb stick displayed in partition layout editor and its dialogs